Previously reported 5bre/intumescent composite textile systems are leading to the development of a range of high performance thermal barrier fabrics. These systems comprise nonwoven cores of 6ame retardant cellulose/regenerated cellulose throughout which 5bre-interactive intumescent chemicals (melamine and phosphate based) are dispersed. When heated, both components decompose by compatible physical and chemical mechanisms leading to a complex carbonaceous 9char-bonded structure:. Mass loss studies of these samples indicate that decomposition takes place in three stages, an initial volatilization, char formation (both occurring during the 5rst 3.5 min exposure period) and a char oxidative stage continuing over a much longer period. Kinetic analysis of mass loss curves gives insight into their thermal behaviour. Thermal insulative properties of these samples have been observed by embedding thermocouples within layers of fabrics and measuring their temperatures as functions of time. Using this technique, a measure of the time dependence of the thermal barrier properties has been gained at heat 6uxes in the range 25}75 kW m ؊2 . Derived thermal resistivity values illustrate the superior barrier properties a4orded by the complex chars formed.